The present disclosure relates to a method for producing a belt such as a V-ribbed belt, a raw edge V-belt, a cogged V-belt, and a toothed belt, and a two-layer bonding machine.
When an uncrosslinked rubber composition containing short fibers is extrusion molded into an uncrosslinked rubber sheet, the short fibers are insufficiently oriented in the uncrosslinked rubber sheet. It is therefore difficult to produce a V-ribbed belt which is inexpensive, unlikely to generate a noise, and has a high wear resistance by using the uncrosslinked rubber sheet. For this reason, in practice, an uncrosslinked rubber sheet for forming V-shaped ribs in which short fibers are oriented in the width direction is prepared in the following manner. An uncrosslinked rubber composition containing the short fibers blended therein is kneaded, and then rolled with a calender to form an uncrosslinked rubber sheet in which the short fibers are oriented in the length direction. Subsequently, the uncrosslinked rubber sheet is cut perpendicularly to the length direction at regular intervals into rubber pieces. The rubber pieces are joined together at its sides, thereby forming the uncrosslinked rubber sheet. However, this method requires use of expensive short fibers, and the orientation of the short fibers must be precisely controlled.
To address this problem, as disclosed in, for example, Japanese Patent No. 5156881, it has been known that an uncrosslinked rubber sheet for a compressed rubber layer is prepared by extrusion molding an uncrosslinked rubber composition which includes no short fibers but contains hollow particles and/or a foaming agent blended therein.
It has also been known to produce, by using a molding method, a V-ribbed belt having rib surfaces covered with canvas which is stretchable in two predetermined directions, wherein a belt matrix permeates through the texture of the canvas (see, for example, Japanese Patent No. 5717810). In this molding method, the rib surfaces press the canvas arranged on the outer periphery of the belt matrix and the belt matrix onto a mold provided on the inner peripheral surface of a shell, and the belt matrix is then crosslinked and molded.